Annular valve

ABSTRACT

A valve assembly ( 1 ) operable to allow or prevent the flow of fluid to or from a working chamber of a fluid-operated machine, comprising radially spaced apart inner and outer annular valve seats ( 8, 15 ) defining an annular passage therebetween, a valve member comprising a sealing ring ( 21 ), and means ( 3, 7, 26, 25 ) for moving the valve member axially between a first position in which the sealing ring ( 21 ) is in seating engagement with the annular valve seats to close the annular passage to fluid flow therethrough and a second position in which the sealing ring ( 21 ) is spaced from the annular valve seats ( 8, 15 ) so that the annular passage is open to fluid flow therethrough. The valve assembly further comprises axially spaced apart first and second valve guide means ( 6 ) for guiding the valve member during axial movement between its first and second positions.

This invention relates to a valve assembly, for example for afluid-operated machine, such as a pump or motor, and in particular tovalve assemblies for large fluid-operated machines which require veryhigh flow rates through induction and delivery valves. The inventionalso relates to a fluid-operated machine provided with such a valveassembly.

It has been common practice, at least with fluid-operated machinesworking at low pressures and compressible flows, such as aircompressors, to use annular plate valves with inner and outer annularpassages to reduce induction pressure drop. However, to date, forhigh-pressure applications, poppet valves for fluid-operated machineshave been limited to a single annular flow path.

Examples of known annular valves are shown in GB-A-251,472,GB-A-1,104,308, U.S. Pat. No. 1,925,464 and U.S. Pat. No. 5,673,656.

An aim of the present invention is to provide a high-pressurefluid-operated machine having an actively controlled annular valvemember, e.g. a poppet valve, for the purpose of flow rectification.

According to one aspect of the present invention there is provided avalve assembly operable to allow or prevent the flow of fluid to or froma working chamber of a fluid-operated machine, the valve assemblycomprising radially spaced apart inner and outer annular valve seatsdefining an annular passage therebetween for the flow of fluidtherethrough, a valve member comprising a sealing ring, means for movingthe valve member axially between a first position in which the sealingring is in seating engagement with said annular valve seats to closesaid annular passage to fluid flow therethrough and a second position inwhich the sealing ring is spaced from said annular valve seats so thatsaid annular passage is open to fluid flow therethrough, and axiallyspaced apart first and second valve guide means for guiding the valvemember during axial movement of the latter between said first and secondpositions.

The use of a valve member having a sealing ring movable into and out ofsimultaneous contact with both the radially inner and outer annularseats permits the creation of two concentric fluid flow passages,effectively doubling the flow area through the valve passage over theconventional form for the same amount of axial valve displacement. Thisfeature permits the pressure drop through a valve assembly of thisconformation to be one quarter that for a similarly sized conventionalpoppet valve assembly.

When the valve member is seated, pressure acts across the area definedbetween the inner and outer circular lines of contact of the sealingring with the inner and outer valve seats. The stress imposed on the“poppet” valve member is therefore much reduced since the core area,defined by the area inside the inner circular seating line of contact,is not part of the valve member and therefore is not subjected to thepressure loading of this region.

Conveniently the valve member further comprises first and second guidemembers positioned on opposite axial sides of the sealing ring, thefirst guide member cooperating with said first guide means and thesecond guide member cooperating with said second guide means. Preferablyat least one of said first guide member and said first guide meanscomprises a cylindrical surface coaxial with the sealing ring.Preferably one of the second guide member and the second guide meanscomprises a coaxially positioned cylindrical member, such as a guidepin, and the other of said second guide member and said second guidemeans comprises a bearing, such as a bearing ring, within which thecylindrical member is received for relative sliding movement.

According to another aspect of the present invention there is provided avalve assembly operable to allow or prevent the flow of fluid to or froma working chamber of a fluid-operated machine, the valve assemblycomprising radially spaced apart inner and outer annular valve seatsdefining an annular passage therebetween for the flow of fluidtherethrough, a valve member comprising a sealing ring, means for movingthe valve member axially between a first position in which the sealingring is in seating engagement with said annular valve seats to closesaid annular passage to fluid flow therethrough and a second position inwhich the sealing ring is spaced from said annular valve seats so thatsaid annular passage is open to fluid flow therethrough, the valvemoving means comprising a ferrous annular moving pole member attached tothe valve member, a permanent magnet arranged to magnetically urge themoving pole member so that the valve member is in its second positionand coil means which can be energised to oppose the magnetic force ofthe permanent magnet acting on the moving pole member to cause the valvemember to move to its first position. The valve member can be actuatedby a strong electric pulse applied to the coil means, e.g. a solenoidcoil, and then retained in its first position by a pulse-width modulatedsignal to reduce energy consumption and heating.

According to a further aspect of the present invention there is provideda valve assembly operable to allow or prevent the flow of fluid to orfrom a working chamber of a fluid-operated machine, the valve assemblycomprising radially spaced apart inner and outer annular valve seatsdefining an annular passage therebetween for the flow of fluidtherethrough, a valve member comprising a sealing ring, means for movingthe valve member axially between a first position in which the sealingring is in seating engagement with said annular valve seats to closesaid annular passage to fluid flow therethrough and a second position inwhich the sealing ring is spaced from said annular valve seats so thatsaid annular passage is open to fluid flow therethrough, the inner andouter valve seats being constructed and arranged to have substantiallythe same axial elasticity.

Suitably the elasticity of the radially outer annular valve seat may bematched to that of the radially inner annular valve seat by designingthe radially outer valve seat to flex or give in the axial direction.This can be accomplished, for example, by physically weakening theradially outer annular valve seat. Typically this is achieved bydesigning the outer annular valve seat to have one or more convolutionsor recesses in its walls.

The valve member, or at least the sealing ring thereof, is suitably madeof a polymeric material or a composite material composed of strongfibres in a polymer matrix so as to have the qualities of low mass, highresistance to creep, high strength, good temperature and fatigueresistance and low absorption of water, oil and other solvents. Theinner and outer valve seats are shaped with smooth curves to giveminimal resistance to both directions of flow.

According to a still further aspect of the present invention there isprovided a valve assembly comprising radially spaced apart inner andouter annular valve seats defining an annular passage therebetween forthe flow of fluid therethrough, a valve member comprising a sealing ringhaving a forward portion and a rearward portion, the sealing ring beingmovable axially between a first position in which the said forwardportion is in seating engagement with said annular valve seats to closesaid annular passage to fluid flow therethrough and a second position inwhich the said forward portion is spaced rearwardly from said annularvalve seats so that said annular passage is open to fluid flowtherethrough, wherein said radially outer valve seat forms part of aradially outer seating surface which, in the direction rearwardly fromsaid radially outer valve seat, has a converging portion part of whichhas a diameter less than that of the radially outer valve seat.

According to a yet further aspect of the present invention there isprovided a fluid-operated machine having a cylinder with a workingchamber and a valve assembly according to any one of said precedingaspects of the invention, the valve assembly being movable between itsfirst and second positions to prevent or allow the flow of fluid throughsaid annular passage to or from the working chamber.

Embodiments of the invention will now be described, by way of exampleonly, with particular reference to the accompanying drawings, in whichFIGS. 1 and 2 are schematic sectional views of two different embodimentsof a valve assembly, according to the present invention, of afluid-operated machine.

FIG. 1 shows a valve assembly, generally designated by the referencenumeral 1, intended to be fitted to the top of a working chamber (notshown) of a fluid-operated machine. The machine in question may be alarge fluid power pump or motor where very high flow rates are requiredthrough the induction and delivery valves. Double headed arrows shown infull lines in the drawing illustrate fluid flow paths, the direction ofthe fluid flows depending on whether the machine operates as a pump ormotor.

The valve assembly 1 has a central steel support 2 which carries asolenoid coil 3 at its upper end. The lower portion of the steel support2 has two axially spaced apart annular portions 4 and 5. The upperannular portion 4 supports a guidance bush 6 having an outer surfacewhich is preferably of circular cylindrical form. The lower annularportion 5 has a permanent magnet 7 fixed, e.g. bonded, to its uppersurface and has a shaped outer surface defining a radially inner annularvalve seat 8. A flux concentrating ring 7 a is bonded to the uppersurface of the magnet 7. An axially positioned guide pin 9 is fixed inan axially located bore at the bottom of the support 2.

A steel element 10 is fixed to the upper end of the support 2 by meansof a bolt 11. The element 10 has a number, e.g. eight, of radiallyextending axial webs or fins 10 a. A compression nut 12 is screwed downonto radially outer portions of these fins 10 a and is screw-threadedlyconnected to a steel shroud 13. By tightening the nut 12 the shroud issecurely retained on the fins 10 a. The lower part of the shroud 13 isshaped on its inner surface to define a radially outer annular valveseat 15. The inner surface of the shroud 13 provided a seating surfacewith a diverging portion 15 a which diverges away from the valve seat 15in the downward axial direction. An additional shroud member 13 a isfixed to the bottom of the shroud 13 and provides, on its radially innersurface, a converging portion 15 b which converges in the downward axialdirection. Thus in the downward axial direction the valve seat 15extends into a diverging surface provided by portion 15 a and aconverging surface provided by portion 15 b. The lower parts of theconverging portion 15 b have diameters less than the diameter of thevalve seat 15. A generally annular fluid flow passage is defined betweenthe radially spaced apart annular valve seats 8 and 15 and extendsupwardly between inner surfaces of the bolt 12 and shroud 13 and outersurfaces of the steel support 2 and the element 10, the radial fins 10 adividing the upper end of the passage into a number of circumferentiallyspaced apart sub-passages.

The valve assembly further comprises a valve member comprising a sealingring 21 having integrally formed therewith an upwardly extendingcylindrical portion 22 and downwardly and inwardly extending ribs 23supporting a bearing ring 24 in which the guide pin 9 is received. Thering 21 has, in cross section, a generally semi-circular upper portion21 a and a tapering lower portion 21 b, the inner surface of which issubstantially parallel with the axis of the ring 21 and the outersurface of which is inwardly inclined in the downward direction.Suitably the sealing ring 21 is made of a polymeric material or acomposite material composed of strong fibres in a polymer matrix and hasthe qualities of low mass, high resistance to creep, high strength, goodtemperature and fatigue resistance and low absorption of water, oil andother solvents. A compression spring 25 is positioned around the pin 9between the bottom of the support 2 and the bearing ring 24. Thecylindrical portion 22 carries an annular ferrous moving pole member 26by means of a number of circumferentially spaced apart radial webs 27.

In operation of the valve assembly 1 the valve member is by default heldin its open position by the permanent magnet latch consisting of theferrous annular moving pole member 26 which is magnetically attracted tothe permanent magnet 7 bonded to the fixed ferrous annular portion 5.The magnetic circuit is such that the path of the magnetic flux (shownin dashed lines) describes a torus and retains the pole member 26 in itsaxially lowermost position so that the sealing ring is spaced from thevalve seats 8 and 15 in an open position. This magnetic retaining forceis designed to be several times greater than the maximum fluid forcewhich acts on the valve during the up-stroke of the piston. In the openposition of the valve member, fluid is able to pass though the annularpassage radially inwardly and outwardly of the sealing ring 21. Theinner and outer valve seats 8 and 15 are shaped with smooth curves togive minimal resistance to both directions of flow. The specific shapingof the ring portion 21 b and the portions 15 a and 15 b are such that,in the open position of the valve member, the portions 15 a and 15 bextend around and beneath the sealing ring 21. In particular the forwardportion 21 a of the sealing ring 21 is spaced from the valve seat 15 adistance substantially the same as the distance of the rearward portion21 b of the sealing ring from the converging portion 15 b. Some portionsof the upwardly flowing (as viewed in FIG. 1) fluid flow over the upperand lower portions 21 a and 21 b of the sealing ring with a similar orcomparable velocity.

The valve member is closed by electrically energising the solenoid coil3 which is coaxial with the support 2 and is positioned radially insidea solenoid outer pole 30 formed by the element 10. The magnetic flux(see the dashed lines) induced in the outer pole 30 crosses the air gapbetween the lower end of the pole 30 and the moving pole member 26 andattracts the latter upwardly whilst also sending flux to oppose thepermanent magnet 7 such that it is largely, but only temporarily,demagnetised. During the solenoid coil actuation the flux in the lowerpart of the moving pole member 26 is so reduced that it loses its holdon the flux concentrating ring 7 a and accelerates towards the solenoidouter pole 30 with the result that the valve member is pulled upwardlyinto its closed position with the sealing ring 21 seating against thevalve seats 8 and 15 and closing the annular passage to prevent fluidflow therethrough. The axial venturi force acting on the valve ring 21to close the valve member against flow is reduced or eliminated by theshaping of the valve ring 21, with its portions 21 a and 21 b, and theportions 15 a and 15 b of the seating surface described above. Thisreduces the force required of the permanent magnetic latch, hencereducing the reaction time of the valve to a solenoid coil pulse andreducing the electrical power consumption.

The valve can be used in a number of configurations: passively latchedopen and actively closed; latched closed and actively opened; andactively opened and closed. In the cases where the actuation isunidirectional, there are further variations. The latch can provide aspring, based on the attraction of a permanent magnet, with acharacteristic force curve following an inverse square law. Mechanicalsprings can be added to the mechanism which superpose on the magneticforce to create different return characteristics.

The inner valve seat 8 is supported on, or provided by, the steel member2 that serves both as a structural member and as a flux path for themagnetic circuit to actuate and latch the valve member. The steelelement 10 is rigidly fixed to the centre of the steel member 2 and hasa solenoid outer pole 30 surrounding the coil. The radial ribs or fins10 a on the outer surface of the element 10 serve to mechanically locatethe inner valve seat, and hold it concentric in the valve passage, whilealso allowing fluid to pass around the valve core with minimaldisruption. It is difficult to prevent the structure, which holds theinner valve seat 8, from allowing a significant axial deflection of thisseat whilst under load, due to the indirect load path through the radialribs. The outer valve seat 15 is more directly attached to therestraining annular compression nut 12 and would normally deflect farless than the inner valve seat 8. In order to keep the loading equal onboth inner and outer sealing lines, the outer valve seat “ring” ispurposefully reduced in axial rigidity by the introduction of aconvolution 32 in its structure. As pressure builds on the closedannular sealing ring 21 or poppet, it will cause both inner and outervalve seats to move equally. This will prevent rolling of the valvesealing ring 21 on the valve seats, which would limit life throughfatigue and galling.

The annular sealing ring 21 is large in diameter relative to its length,which could cause difficulties with jamming and friction. For thisreason two guidance bearings have been incorporated to ensure that thepoppet motion is free of stiction and governed by the flow and latchforces alone. The first guidance bearing acts between the inside of themoving pole ring 26 and the cylindrical outer surface of the bush 6,which is suitably a stationary polymer disc, and which could also beintegral with the coil bobbin. This guide ensures that the moving pole26 maintains a consistent radial gap relative to the magnetic pole ridgeon the inner seat member 2 and so prevents excessive unbalanced radialmagnetic forces from building up.

The second guide is axially spaced from the first guide and is providedby the guide pin 9 and bearing ring 24 located below the sealing ring21. The pin 9 is suitably formed of a hard metal. The radial fins 23attached on their outer ends to the sealing ring 21 join onto thebearing ring 24. It is envisioned that the sealing ring 21, the fins 23and the bearing ring 24 will be integrally moulded. The two guides will,in combination, constrain the poppet in all axes of motion other thanthe axial one, in which it must move to open and close, and therotational one, which is of no concern. The mechanical spring 25 acts onthe bearing ring 24 to speed the opening of the valve when the coil isde-energised and the sealing ring 21 is no longer held closed bypressure.

FIG. 2 illustrates an alternative embodiment of a valve assembly 51according to the invention. In the two valve assemblies shown in FIGS. 1and 2 the same reference numerals have been used to identify similarparts. The differences between the two designs are that in FIG. 2 thevalve ring 2 has a substantially circular cross section and the lowershroud part 13 b is not provided.

1. A valve assembly operable to allow or prevent the flow of fluid to orfrom a working chamber of a fluid-operated machine, the valve assemblycomprising radially spaced apart inner and outer annular valve seatsdefining an annular passage therebetween for the flow of fluidtherethrough, a valve member comprising a sealing ring, and valve movingapparatus for moving the valve member axially between a first positionin which the sealing ring is in seating engagement with said annularvalve seats to close said annular passage to fluid flow therethrough anda second position in which the sealing ring is spaced from said annularvalve seats so that said annular passage is open to fluid flowtherethrough, wherein the valve assembly further comprises axiallyspaced apart first and second valve guide for guiding the valve memberduring axial movement of the latter between said first and secondpositions.
 2. A valve assembly according to claim 1, wherein the valvemember further comprises first and second guide members positioned onopposite axial sides of the sealing ring, the first guide membercooperating with said first guide and the second guide memberscooperating with said second guide.
 3. A valve assembly according toclaim 2, wherein at least one of said first guide member and said firstguide comprises a cylindrical surface coaxial with the sealing ring. 4.A valve assembly according to claim 2, wherein one of the second guidemember and the second guide comprises a coaxially positioned cylindricalmember and the other of said second guide member and said second guidecomprises a bearing within which the cylindrical members is received forrelative sliding movement.
 5. A valve assembly operable to allow orprevent the flow of fluid to or from a working chamber of afluid-operated machine, the valve assembly comprising radially spacedapart inner and outer annular valve seats defining an annular passagetherebetween for the flow of fluid therethrough, a valve membercomprising a sealing ring, valve moving apparatus for moving the valvemember axially between a first position in which the sealing ring is inseating engagement with said annular valve seats to close said annularpassage to fluid flow therethrough and a second position in which thesealing ring is spaced from said annular valve seats so that saidannular passage is open to fluid flow therethrough, wherein the valvemoving apparatus comprises a ferrous annular moving pole member attachedto the valve member, a permanent magnet arranged to magnetically urgethe moving pole members so that the valve member is in its secondposition and an electromagnetic coil which can be energised to opposethe magnetic force of the permanent magnets acting on the moving polemember to cause the valve member to move to its first position.
 6. Avalve assembly operable to allow or prevent the flow of fluid to or froma working chamber of a fluid-operated machine, the valve assemblycomprising radially spaced apart inner and outer annular valve seatsdefining an annular passage therebetween for the flow of fluidtherethrough, a valve member comprising a sealing ring, valve movingapparatus for moving the valve member axially between a first positionin which the sealing ring is in seating engagement with said annularvalve seats to close said annular passage to fluid flow therethrough anda second position in which the sealing ring is spaced from said annularvalve seats so that said annular passage is open to fluid flowtherethrough, wherein the inner and outer valve seats are constructedand arranged to have substantially the same axial elasticity.
 7. A valveassembly according to claim 6, wherein the elasticity of the radiallyouter annular valve seat is matched to that of the radially innerannular valve seat by designing the radially outer valve seat to flex orgive in the axial direction.
 8. A valve assembly according to claim 7,wherein the radially outer annular valve seat has weakened portions. 9.A valve assembly according to claim 7, wherein the outer annular valveseat is provided with one or more convolutions or recesses in its walls.10. A valve assembly according to claim 1, wherein said sealing memberis made of a polymeric material.
 11. A valve assembly according to claim1, wherein said radially outer valve seat forms part of a radially outerseating surface which, in the direction rearwardly from said radiallyouter valve seat, has a converging portion part of which has a diameterless than that of the radially outer valve seat.
 12. A valve assemblycomprising radially spaced apart inner and outer annular valve seatsdefining an annular passage therebetween for the flow of fluidtherethrough, a valve member comprising a sealing ring having a forwardportion and a rearward portion, the sealing ring being movable axiallybetween a first position in which the said forward portion is in seatingengagement with said annular valve seats to close said annular passageto fluid flow therethrough and a second position in which the saidforward portion is spaced rearwardly from said annular valve seats sothat said annular passage is open to fluid flow therethrough, whereinsaid radially outer valve seat forms part of a radially outer seatingsurface which, in the direction rearwardly from said radially outervalve seat, has a converging portion part of which has a diameter lessthan that of the radially outer valve seat.
 13. A valve assemblyaccording to claim 12, wherein said radially outer seating surface has adiverging portion extending rearwardly of said radially outer valve seatand positioned forwardly of said converging portion.
 14. A valveassembly according to claim 12, wherein when the valve member is in itssecond position the said forward portion of the sealing ring is spacedapart from the radially outer valve seat a distance substantially thesame as the said rearward portion of the sealing ring is spaced from thesaid converging portion of the radially outer seating surface.
 15. Afluid-operated machine having a cylinder with a working chamber and avalve assembly according to claim 1, the valve assembly being movablebetween its first and second positions to prevent or allow the flow offluid through said annular passage to or from the working chamber.